Safety devices such as and without limitation inflatable restraint assemblies, seat belts, and rollover bars are used within vehicles to reduce the likelihood of injury to occupants of the vehicle in the event of a vehicle rollover or collision. It is desirable to determine when a vehicle rollover is imminent or relatively certain to occur so that these safety devices can be selectively activated or engaged prior to or substantially contemporaneous with the occurrence of a rollover in order to protect the occupants of the vehicle; and to substantially prevent and/or reduce the likelihood of an unnecessary activation since many of these devices must be replaced after they have activated, resulting in a significant expense and an annoyance to a vehicle owner.
For example and without limitation, inflatable restraint assemblies, commonly referred to as "air bags" or "curtains", are typically deployed within a vehicle and selectively and inflatably expand into the passenger compartment of the vehicle when the vehicle is struck by or collides with another vehicle or object, and/or "rolls over". These expandable assemblies provide some protection of the vehicle's occupants from injury by protecting the occupants from impacting or "crashing into" the dashboard, windshield, and/or various other portions of the vehicle, and/or from being launched from the vehicle. In order for a vehicle's air bags to provide this desired protection, the air bags must be activated or inflated by way of a pyrotechnic charge or device prior to and/or substantially contemporaneous with the vehicle rolling over.
Vehicle safety belt pretensioning devices or "pretensioners" tighten, lock, and/or remove slack within the vehicle's seat belts during a collision or rollover. These devices must be activated substantially before the vehicle rolls over in order to allow the seat belts to properly restrain the occupants of the vehicle, and to protect the occupants from striking or impacting objects or structures within the vehicle such as the windshield, windows, roofline, or steering wheel, and/or from being launched from the vehicle.
Efforts have been made to detect when a vehicle rollover situation is imminent or relatively certain to occur, and to activate the appropriate safety devices (e.g. the air bags and/or seat belt pretensioners) upon such a detection. Some prior efforts include measuring and/or monitoring the vehicle's acceleration in various directions and/or the angle of the vehicle with respect to the road surface. One drawback associated with these types of prior systems is that they do not adequately ensure that the inflatable devices become energized only when they are actually needed. As such, many of these prior devices activate unnecessarily (e.g., when a rollover is not imminent or relatively certain to occur), and therefore must be replaced or "reset" which, as previously explained, results in an unnecessary and a relatively significant expense to the owner of the vehicle. Furthermore, many of these devices do not account for the fact that vehicles are generally more likely to roll over with a lesser rate of angular variation if the vehicle is already disposed at a certain angle from the road surface. Hence, these devices often do not activate in time to provide the desired protection of the vehicle occupants.
Applicant's invention addresses these drawbacks and provides a method and an apparatus for detecting a vehicle rollover which employs multiple sensors to gather data relating to the acceleration and/or rate of angular change of the vehicle in multiple directions; which analyzes the data to determine whether a vehicle rollover situation is imminent or relatively certain to occur; and which selectively and reliably activates one or more vehicle safety devices in response to the detection of a rollover situation.